单轴压缩条件下原生微裂隙对白云岩力学特性的影响规律研究

发布时间：2018-05-20 12:49

本文选题：岩石力学 + 大开孔隙率　；参考：《昆明理工大学》2015年硕士论文

【摘要】：岩石是自然界中一种复杂的天然介质,由于成岩作用和成岩环境的差异,其内部孕育着大量的节理、裂纹、微裂隙等缺陷,对含节理、裂隙等缺陷岩石力学特性的研究成为近年来工程界和岩石力学界所重点关注的内容。通过试验的方法开展对含裂隙岩石材料力学特性的研究,对确保含裂隙岩石工程的稳定与安全具有重要的现实意义。鉴于此,结合工程应用的实际需要,本文依托国家自然科学基金项目“频繁强振和高应力环境下深部节理化岩巷变形累积转化特征及其失稳机理(项目编号：41362013)”,为研究原生微裂隙对白云岩力学特性的影响规律和破坏模式,对含有不同微裂隙的白云岩进行单轴压缩实验。实验前,利用声波法和自然吸水法对含微裂隙白云岩试件进行声波波速与大开孔隙率的测试,以反映其内部隐微裂隙的发育程度。在此基础上,对含原生微裂隙的白云岩进行单轴压缩试验,研究含原生微裂隙白云岩的宏观力学特性及变形破坏特征,探讨白云岩强度、弹性模量、泊松比、声发射特征及破坏特性与裂隙发育程度的关系,揭示单轴压缩条件下原生微裂隙对白云岩力学特性的影响规律,获得的主要结论如下所述：(1)微裂隙的存在确实减弱了声波在岩石介质中传播的速度,随着岩石试件大开孔隙率的增加,微裂隙对其纵波波速的减弱作用逐渐减小,即声波在含裂隙岩石中传播时表现出明显的“裂隙效应”。通过拟合发现,白云岩试件的声波(纵波)波速与其大开孔隙率呈良好的对数递减的关系。(2)分析统计到的白云岩试样圆周表面微裂隙的初始形态及参数,利用分形几何学的研究方法,对微裂隙的分形维数进行计算并绘制出分形维数与微裂隙数量密度和长度密度的关系曲线,发现微裂隙的分形维数与其数量密度、长度密度均成线性递增的变化规律,说明岩石表面的微裂隙具备良好的分形特征。(3)对白云岩试样在单轴压缩条件下的试验结果进行了分析,通过得到的单轴压缩下白云岩试样的应力-应变曲线,研究了其强度特性、变形特性和声发射特性。微裂隙对白云岩的强度和变形特性产生显著的影响,白云岩的单轴抗压强度、弹性模量均表现出随着大开孔隙率的增大而减小的总体趋势,且降低幅度呈现出由大逐渐变小的规律,但从本次试验获得的数据来看,泊松比随着大开孔隙率的增大没有表现出明显的变化规律。(4)通过对白云岩试样最终破坏形态的分析,从本次试验来看,发现含天然微裂隙白云岩试件在单轴压缩作用下存在张拉破坏、拉剪复合破坏和沿裂隙弱面剪切破坏三种类型的宏观破裂面,经分析后发现,原始微裂隙的分布状态对单轴压缩条件下白云岩试样的具体破坏模式有较大的影响。(5)对单轴压缩条件下白云岩的微裂隙损伤演化过程进行了整体分析,得出试样在受压过程中裂纹的起裂顺序、扩展、和贯通等情况会因初始微裂隙的几何分布的不同有较大的差异。
[Abstract]:Rock is a complex natural medium in nature. Due to the difference between diagenesis and diagenetic environment, the rock has a large number of defects, such as joints, cracks, micro cracks and so on. The research on the mechanical properties of defects, such as joints and cracks, has become a major concern in the field of engineering and rock rock force in recent years. The study of the mechanical properties of fractured rock materials is of great practical significance for ensuring the stability and safety of fractured rock engineering. In view of the actual needs of the engineering application, this paper relies on the National Natural Science Foundation Project "the deformation accumulation and transformation characteristics of the deep jointed rock roadway under the frequent strong vibration and high stress environment." The mechanism of instability (item number: 41362013) ", in order to study the influence law and failure mode of the primary microcracks on the mechanical properties of dolomite, the uniaxial compression test of dolomite with different micro cracks was carried out. Before experiments, the acoustic wave velocity and the large open porosity were tested by sound wave method and natural water absorption method. In order to reflect the development degree of the internal microfracture, the uniaxial compression test of dolomite containing primary microfracture was carried out on this basis, and the macroscopic mechanical properties and deformation and failure characteristics of the dolomite containing primary microfracture were studied, and the intensity, modulus of elasticity, Poisson's ratio, acoustic emission and fracture development of dolomite were discussed. The main conclusions obtained are as follows: (1) the existence of micro fissure does weaken the velocity of sound wave propagation in the rock medium. With the increase of the porosity of the rock specimen, the weakening effect of the micro fissure on its longitudinal wave velocity decreases gradually. Sound waves show a clear "fissure effect" in the propagation of fractured rocks. Through fitting, it is found that the acoustic (P-wave) wave velocity of the dolomite specimen has a good logarithmic decrease in the large open porosity. (2) the analysis of the initial morphology and parameters of the circumferential surface microcracks of the dolomite specimen and the study of the fractal geometry The fractal dimension of the micro fissure is calculated and the relation curve of the number density and the length density of the micro fissure is drawn. It is found that the fractal dimension of the micro fissure is linearly increasing with the number density and the length density, which shows that the micro fissure of the rock surface has good fractal characteristics. (3) the dolomite sample The experimental results under uniaxial compression are analyzed. The strength and deformation characteristics and acoustic emission characteristics of the dolomite are studied by the stress-strain curves of the dolomite samples under uniaxial compression. The micro fissure has a significant influence on the strength and deformation characteristics of dolomite. The uniaxial compressive strength and modulus of elasticity of dolomite are all manifested. The general tendency to decrease with the increase of the porosity of large open porosity and the decreasing amplitude shows the law of gradually decreasing, but from the data obtained in this experiment, the Poisson's ratio does not show obvious change law with the increase of the large open porosity. (4) through the analysis of the final destruction form of the dolomite specimen, this test comes from this test. It is found that there are three types of macroscopic fracture surface, including tensile failure, tensile shear composite failure and shear failure along fissures, and it is found that the distribution state of the original microfracture has a great influence on the concrete failure mode of the dolomite specimen under uniaxial compression. (5) The evolution process of the micro fracture damage of dolomite under uniaxial compression is analyzed. It is concluded that the crack initiation sequence, expansion and penetration of the specimen in the compression process are different because of the difference in the geometric distribution of the initial microcracks.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU452

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